[ARC5] A.C. Modified BC-348

[J Mcvey]

 Sure, that's a standard transformer isolated design using a 5Y3.Safe as it gets.
I would like to see why they used a 25Z5 on the other setup.Makes one go hmmmm....

    On Saturday, August 28, 2021, 12:52:12 PM EDT, Rich Post <kb8tad at gmail.com> wrote:  
 
 Mike is correct relative to the ease of use of the 25Z5 with a transformer designed for directly powering the BC-348 filament string at 24-28 volts.  The instruction sheet says Signal Corps.  Did Hallicrafters produce both an Army version and a Navy version?
My EP-298 power supply uses a 5Y3 rectifier and has the Navy acceptance stamp.<https://people.ohio.edu/postr/bapix/BC348Q_3.htm>
Rich KB8TAD


On Sat, Aug 28, 2021 at 12:08 PM Michael Hanz <aaf-radio-1 at aafradio.org> wrote:

  Schematic attached.  There were apparently two different rectifier tubes used in the EP-298 Halli supply - initially a 5Y3GT, then a 6X5GT-G - which has a separate cathode independent of the filaments.  It is not hard to anticipate the eventual substitution of a 25Z5 to eliminate the filament winding in the transformer...
 
 No "safety" issues with that design.
 
 On 8/28/2021 10:41 AM, J Mcvey via ARC5 wrote:
  
  A 25Z5 implies a "series string/ hot chassis circuit. The BC348 design does not lend itself very well  to a transformerless power supply. Then again, Hallicrafters was famous for grounding one side of the AC supply to the chassis!. This kind of mod is unsafe, IMO. However, safety did not seem to be a big concern "back in the day"...
  
      On Saturday, August 28, 2021, 12:29:46 AM EDT, Hubert Miller <kargo_cult at msn.com> wrote:  
  
     Here's a 348 i found in my stash. The rectifier tube is a 25Z5, which means a drop -in supply with minimum mods. Unfortunately tho, the cabinet top has been aerated. The PS has no markings really except for this on the tube area shield: "TESTED GOOD 11/10/ 45 ROB". Too early to have hit the surplus stores, so this must be a gov't mod. -Hue Miller 
  
  
  
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